The proposed research will involve investigation of function of human circulating phagocytes, i.e., polymorphonuclear neutrophils and monocytes. The functional assays will include chemotatic responsiveness, phagocytosis and oxidative metabolic response. The methods used for these studies will include measurement of chemotaxis of separated neutrophils and monocytes by migration through millipore filters and migration under agarose. The kinetics of phagocytosis will be studied using radiolabeled pneumococci, staphylococci and E. coli. The metabolic response during phagocytosis will be investigated by recording the chemiluminescence response, oxygen uptake and production of oxygen metabolites during phagocytosis. These methods will be applied to studied of neutrophils and monocytes from patients with increased susceptibility to infection including newborn infants, patients with allergic diseases, patients with recurrent severe infections referred for evaluation of immune function, and patients receiving immunosuppressive therapy. BIBLIOGRAPHIC REFERENCES: Hill, H.R., Mitchell, T.G., Hogan, N.A. and Quie, P.G.: Evaluation of a cytocentrifuge method for measuring neutrophil granulocyte chemotaxis. J. Lab. Clin. Med., 86:703-710, 1975. Van Scoy, R.E., Hill, H.R., Ritts, R.E., Jr., and Quie, P.G.: Familial Neutrophil Chemotaxis Defect, Recurrent Bacterial Infections, Mucocutaneous Candidiasis and Hyperimmunoglobulin E. Ann. Int. Med., 82:766-771, 1975.